I would not dye that often. The roots likely are not noticeable to anyone but youself after just one day. There may be an option for some type of brush in cover up for the roots that show, but most of the ones I have seen are for going darker, not lighter.

My Beard Journey:  http://jefffsbeardboard.yuku.com/topic/25137/Finally-I-have-a-Beard
Beard and Bald Thread:  http://jefffsbeardboard.yuku.com/topic/27831/Beard-bald-head-shaved-head-or-buzzcut
Patchy Beard Success Stories:  http://jefffsbeardboard.yuku.com/topic/33742/Patchy-Beard-success-stories-Before-and-After-photos#.ViujbH7nuM8
Taming the Wild Mustache:  http://jefffsbeardboard.yuku.com/topic/30822/Taming-the-Wild-Stache#.Vj_Mh7erTIU